Kate Spade LLC is getting a management makeover, as it seeks to expand beyond its roots as a boutique label known for its signature handbags, The Post has learned.

Andy Spade, who founded the company in 1993 with his wife Kate, the designer, is to relinquish his post as chief executive, though he plans to continue as creative director, sources said.

Search firm Herbert Mines has been retained to find a new CEO, these people continued.

The planned management change comes on the heels of a half dozen new product launches and as the once-red hot demand for Kate’s quirky, rectangular handbags has cooled, observers said.

The nylon bags were once a must-have for fashionistas but more recently have been eclipsed by fresher styles from the likes of Coach and Marc Jacobs.

In response, Kate Spade has rolled out updated styles in leather and canvas and has branched into new product categories like shoes, eyewear, beauty products, bedding and tableware.

The Neiman Marcus Group bought a majority stake in Kate Spade in 1999, and there is speculation that the retailer has urged the Spades to bring in a seasoned executive to take the company to the next level.

“Kate Spade hasn’t been the resounding success that Neiman Marcus thought it would be,” one source said.

Andy Spade was on a plane and unavailable for comment.

A spokesman for Herbert Mines declined to comment. A Neiman Marcus spokesman also declined to comment.

Kate Spade has recovered from a low point in 2002, when Neiman Marcus’s “other segment,” which includes Kate Spade and cosmetics brand Laura Mercier, saw operating losses balloon to $19 million, from $8 million the year earlier.

The division is still losing money – $17 million in the 39 weeks that ended May 1 – but sales have grown to $81 million, up 37 percent from the same period a year ago.

Much of the sales growth can be attributed to new Kate Spade product launches, especially bedding and tableware, which have been well received, analysts said.

“Kate Spade was incredibly hot with the nylon handbags, but then leather came back and they didn’t really have a product,” said Eric Beder, an analyst with JB Hanauer & Co.

“In the last year or so, they’ve introduced new lines, and that’s really helped them grow into more of a lifestyle brand,” Beder continued.

Analysts generally give Andy high marks for helping to steer Kate Spade through the transition, but they also concede that it may be the right time for a change.

“As the company gets bigger,” Beder said, “it needs a deeper, more professional management team.”